I would argue that presenting at a national conference is pretty unique. As far as I can tell, few undergraduates have them -- even fewer than publications because the most common way for undergraduates to get published is to do a few months of bench work/clinical data grabbing for their PI to get published as a late author. Actually presenting at a national conference means you did most/all of the work at a high level.
While any publication may be worth more in the eyes of adcoms, I just find it more rare that an undergraduate presents at a national conference, and might draw the attention of one or more faculty members on the committee who are in that field.
Regarding OP, a presentation is beneficial because it demonstrates some quantifiable output to your research. You would need to contact faculty at your institution about doing research with them first, and see if you can spin a part of your project into its own poster.
